Form PA102.20-N1
93
Installation & Assembly Manual │
PACE
SECTION 3 - HANDLING, STORAGE, AND INSTALLATION
Issue Date: 07/03/2018
3
DRAINS AND TRAPS
Where there is a risk of the liquid freez-
ing in the trap, heat trace and insulate
the traps to prevent blockage and/or
damage.
Auxiliary drain pans may not require
traps. If the trap is not in constant use,
the water seal may evaporate, causing air
passage into or out of the AHU. In these
cases, it is recommended to cap the
drain that allows the opening or closing
of the drain, depending on its use.
Condensate Drain Piping
The majority of cooling coils are located in the AHUs,
so that the supply air is drawn through them, which
results in the condensate being subjected to negative
(-) static pressure. Unless pressure equalization is
provided in the condensate drain, the air rushing back
through the drain pipe will cause the condensate to
build up in the drain pan.
As the AHU continues to operate, the accumulated
water will be carried with the air stream, overfilling the
drain pan, causing possible water leaks into the sup-
ply duct and/or causing water damage in the building.
Install a trap to prevent this condensate water buildup
Figure 152 -
Drain Trap Showing Water Location for
Draw Through Operation
LD06342
Drain
Pan
Drain
Nipple
Drain
Pan
Drain
Pan
NO.1 - Fan Off
NO. 2 - Trap Condition When Fan Starts
NO. 3 - Fan Running And Condensate
Cooling Coil
Drain Pan
Trap
Figure 153 -
Trap Detail for Drain Pan in Negative
Environment (Draw Through)
LD05370
H Must Be At Least
1 Plus Fan Total
Static Pressure
H
X= 1/2 H
X
Condensate Drain Trap
For Draw Through
applications, install a trapped con-
densate drain line at the AHU drain connection as
shown in
according to all
codes. The
H
dimension must be at least 1 in. greater
than the design TSP of the fan, which ensures proper
drainage even if filters clog or dampers malfunction.
For Blow Through applications, the same principles ap-
ply, but the leaving pipe should be as shown in
for proper trap design.
Figure 154 -
Trap Detail for Drain Pan in Positive
Environment (Blow Through)
LD05371
H Must Be A Least 1 Inch Plus
Fan Total Static Pressure
H
Top Of Trap Must Be Equal To Or Lower
Than Bottom Of Unit Drain Connection
Drain
Connection
Two or more drains on the same side of AHU must be
trapped individually before the drain lines can be com-
bined and routed to a suitable drain as shown in
